WO2005124907A1

WO2005124907A1 - Porous electrode base material and process for producing the same

Info

Publication number: WO2005124907A1
Application number: PCT/JP2005/011380
Authority: WO
Inventors: Makoto Nakamura; Hidehiko Ohashi; Mitsuo Hamada; Kazushige Mihara; Kazuhiro Sumioka
Original assignee: Mitsubishi Rayon Co., Ltd.
Priority date: 2004-06-21
Filing date: 2005-06-21
Publication date: 2005-12-29
Also published as: EP1788651B1; EP1788651A1; EP1788651A4; US20080038589A1

Abstract

An electrode base material for solid polymer fuel cell that overcomes the problems of prior art and is most suitable for use in assembling of an inexpensive compact cell stack; and a process for producing the electrode base material. There is provided a porous electrode base material of ≤ 150 μm thickness, comprising carbon staple fibers of 3 to 9 μm diameter dispersed in random directions within a substantially two-dimensional plane, these carbon staple fibers bound to each other by an amorphous resin carbide, further these carbon staple fibers crosslinked to each other by a filamentous resin carbide. It is also intended to provide an electrode base material for solid polymer fuel cell that overcomes the problems of prior art, realizing low cost, smooth supply and discharge of gas and water for use in reaction and exertion of cell performance. Thus, further, there is provided a porous electrode base material of ≤ 150 μm thickness, comprising carbon staple fibers of 3 to 9 μm diameter dispersed in random directions within a substantially two-dimensional plane, these carbon staple fibers bound to each other by an amorphous resin carbide, further these carbon staple fibers crosslinked to each other by a network resin carbide of ≤ 3 μm minimum fiber diameter.

Description

Porous electrode substrate and method for producing the same

Technical field

The present invention relates to a porous electrode substrate and a method for producing the same.

Background art

[0002] A porous electrode substrate is a member located between a separator and a catalyst layer in a polymer electrolyte fuel cell. This material not only functions as an electric carrier between the separator and the catalyst layer, but also distributes gas such as hydrogen and oxygen supplied from the separator to the catalyst layer and absorbs water generated in the catalyst layer and discharges it to the outside. It is required to have the function of At present, carbonaceous materials are generally considered effective.

Conventionally, in order to increase the mechanical strength, methods such as tight binding of short carbon fiber and resin carbide were used.The gas permeability decreased, and the performance when assembled into a fuel cell was reduced. I had a lot to fall. On the other hand, if the gas permeability was to be maintained at a high level, the mechanical strength was weakened and the handling method was limited.

[0003] Patent Document 1 describes a porous electrode substrate in which organic fibers are used and pores are formed by using the fact that the organic fibers disappear by carbonization of the electrode substrate. However, the pores thus formed have a high porosity but an average diameter, and their gas permeability is too low for use in a polymer electrolyte fuel cell. In addition, there was a problem that the thickness was large and the cost was high.

Patent Document 2 describes a method for manufacturing an inexpensive porous electrode substrate. In the porous electrode substrate obtained by this method, since the web is also oriented in the thickness direction, the conductivity and gas permeability in the thickness direction are satisfactory values, but in the thickness direction where the mechanical strength is weak. There were issues in handling, such as the oriented fibers breaking through the electrolyte membrane and making them brittle once pressed.

Patent Document 3 describes a porous electrode substrate having a pore volume of 0.05 to 0.16 cc Zg with a pore diameter of 10 m or less in order to prevent cracking of the porous carbon substrate and increase mechanical strength. Have been. If the pore size is less than 10 / zm, water retention is It is considered that the power generation of the fuel cell, which is difficult to control due to its small size, cannot be performed sufficiently.

Patent Document 1: Japanese Patent Application Laid-Open No. 9-278558

Patent Document 2: Japanese Patent Publication No. WO2001Z04980 (Patent Table 2003—504822 Publication)

Patent Document 3: WO2004Z085728

Disclosure of the invention

Problems to be solved by the invention

[0005] The first and second inventions overcome the above-mentioned problems and are inexpensive, compact, and optimally suitable for assembling a cell stack. The object of the present invention is to provide a method for producing an electrode substrate.

In addition, the third and fourth inventions overcome the above-mentioned problems, and are capable of smoothly supplying and discharging water and gas used for the reaction at low cost, and exhibiting cell performance. It is an object to provide an electrode substrate for use and a method for producing the electrode substrate. Means for solving the problem

[0006] The gist of the first invention is that short carbon fibers having a fiber diameter of 3 to 9 µm dispersed in a random direction substantially in a two-dimensional plane are bound to each other with an amorphous resin carbide, Further, there is provided a porous electrode base material having a thickness of 150 m or less, wherein the short carbon fibers are crosslinked with each other by a filamentous grease carbide.

The gist of the second invention is that after impregnating a carbon fiber paper having a carbon fiber weight of 16 to 40 g Zm ² comprising a carbon short fiber having a fiber diameter of 3 to 9 m and vinylon fiber with a resin (preferably, a carbon fiber After impregnating carbon fiber paper of 8 to ²⁰ gZm ² with resin and stacking two sheets), it is a method for producing a porous electrode base material that is carbonized.

[0007] The gist of the third invention is that short carbon fibers having a fiber diameter of 3 to 9 μm dispersed in a random direction in a substantially two-dimensional plane are bound together by an amorphous resin carbide, Further, the above-mentioned porous electrode base material is such that the short carbon fibers are crosslinked with a mesh-like resin carbide having a minimum fiber diameter of 3 μm or less.

The gist of the fourth invention is that a short carbon fiber having a fiber diameter of 3 to 9 μm dispersed in a random direction in a substantially two-dimensional plane, and a freeness other than fibrous fiber of 400 are used.

~ 900ml of fibril, carbon fiber paper impregnated with grease and then greased into carbon In a method for producing a porous electrode substrate to be converted.

The invention's effect

[0008] According to the first invention, it is possible to obtain a porous electrode substrate having a gas permeability of a satisfactory value and excellent bending strength while being thin and inexpensive. Further, according to the method for producing a porous electrode substrate of the second invention, the porous electrode substrate can be produced at low cost.

According to the third invention, a polymer electrolyte fuel cell which overcomes the above-mentioned problems, is inexpensive, can smoothly supply and discharge water and gas used for the reaction, and can exhibit cell performance. An electrode substrate can be obtained. Further, according to the method for producing a porous electrode substrate of the fourth invention, the porous electrode substrate can be produced at low cost.

Brief Description of Drawings

FIG. 1 is an electron micrograph of the surface of a porous electrode substrate of the first invention.

FIG. 2 is an electron micrograph of the surface of the porous electrode substrate of the first invention. The magnification is higher than in FIG.

FIG. 3 is a graph showing the pore size distribution of the porous electrode substrate of the first invention.

FIG. 4 is an electron micrograph of the surface of a porous electrode substrate of the third invention (Example 8).

FIG. 5 is an electron micrograph of the surface of a porous electrode substrate of the third invention (Example 9).

FIG. 6 is an electron micrograph of the surface of a porous electrode substrate of the third invention (Example 10).

FIG. 7 is an electron micrograph of the surface of a porous electrode substrate of Comparative Example 5.

FIG. 8 is a graph showing a pore distribution of a porous electrode substrate according to a third invention (Example 8). Comparative Example 4 was compared with the measurement result.

FIG. 9 shows the results of evaluating the battery characteristics of the porous electrode substrate of the third invention (Example 8). This was compared with the measurement result of Comparative Example 4.

BEST MODE FOR CARRYING OUT THE INVENTION

[0010] "First and Second Inventions"

Embodiments of the first and second inventions will be described below with reference to the drawings.

The carbon fiber which is the raw material of the short carbon fiber used in the present invention is polyacrylonitrile-based carbon. Fibers, pitch-based carbon fibers, rayon-based carbon fibers, etc. may be used, but polyatali-tolyl-based carbon fibers are preferred.In particular, only polyacrylonitrile (PAN) -based carbon fibers can be used. Preferred because the mechanical strength of the carbon electrode substrate can be relatively high! /.

The diameter of the short carbon fiber should be 3 to 9 / ζπι, the production cost of the short carbon fiber, the dispersibility and the surface smoothness of the final porous electrode substrate are also required. It is preferably not more than μm.

The fiber length of the short carbon fiber is preferably from 2 to 12 mm from the viewpoint of binding to a binder described below and dispersibility.

[0011] <dispersion>

In the present invention, `` substantially dispersed in a two-dimensional plane in a random direction '' means that short carbon fibers lie so as to form substantially one surface! / That means. As a result, short-circuiting due to short carbon fibers and breakage of short carbon fibers can be prevented.

[0012] <Lead carbide>

In the present invention, the carbonized resin is a substance formed by carbonizing the resin and binding short carbon fibers. As the resin, phenol resin such as phenol resin, which has a strong binding force with carbon fibers and has a large residual weight during carbonization, is preferred, but is not particularly limited.

Depending on the type of the resin and the amount of impregnation into the carbon fiber paper, the ratio of the resin carbide finally remaining as a carbide on the porous electrode substrate varies.

When the porous electrode substrate is taken as 100% by mass, the lower limit and the upper limit are more preferably 28% by mass and 34% by mass, respectively.

In order to completely bind the short carbon fibers and keep the mechanical strength of the porous electrode substrate sufficient, 25% by mass or more of the resin carbide is required. The short carbon fibers that are not completely bound may fall off from the porous electrode base material, stick to the electrolyte membrane, and cause a short circuit. On the other hand, it is advantageous to keep the proportion of short carbon fibers in the porous electrode base material high, and set it to 40% by mass or less so that the pores are not filled with the resin due to the pressure applied during the curing of the resin. It is. [0013] <Amorphous fatty carbide>

In the present invention, first, it is necessary that short carbon fibers are bound together with an amorphous resin carbide as in a conventional porous electrode substrate.

[0014] <Filamentary resin carbide>

In the present invention, from the viewpoint of achieving both mechanical strength and control of the reaction gas and moisture together with the amorphous resin carbide, it is necessary to have a filamentous resin carbide bridging the short carbon fiber and the short carbon fiber. is there.

This filament-like resin carbide has a different appearance from short carbon fibers, and the carbon constituting the filament-like resin carbide has a very good carbon orientation in the short carbon fibers. On the other hand, it is the same as the above-mentioned irregular-shaped fatty carbide.

Figures 1 and 2 show how short carbon fibers and short carbon fibers are cross-linked with filamentary carbonized carbide. Filamentous carbonized carbide provides a porous electrode substrate with high mechanical strength even though it is thin. The reason for this is that the filament-like resin carbide also exerts the same reinforcing effect as the short carbon fiber, and thus the ratio of the short carbon fiber contained in the porous electrode base material can be reduced. Can be provided at cost.

At the same time, some large pores are divided by the cross-linking of the filamentous resin carbide, so that the porous electrode substrate of the present invention has pores with a radius of 5 μm or less and pores with a radius of 25 μm or more. It also has a wide pore size distribution, such as Accordingly, the porous electrode substrate of the present invention has both a function of smoothly discharging the reaction gas and generated water from the porous electrode substrate and a water retaining property of preventing the electrolyte membrane from drying and reducing the efficiency of the reaction. The former function is performed by large pores of 25 m or more, and the latter function is performed by relatively small pores of 5 m or less. Such a wide pore diameter distribution range is advantageous for achieving both functions required of a porous electrode substrate.

[0015] <thickness>

The porous electrode substrate of the present invention needs to have a thickness of 150 μm or less, preferably 140 μm or less, and more preferably 130 μm or less. Porous electrode substrates with a thickness of more than 150 μm have also been used, but this is not desirable in terms of reducing the cost and size of cell stacks in the future. The electric resistance in the penetrating direction can be reduced as the thickness is reduced. The porous electrode base material has a small thickness! /, So that the flow rate of the reaction gas is easily maintained, so that the performance of the entire cell is stabilized.

[0016] <Bending rupture load>

A feature of the present invention is that despite having such a thin porous electrode substrate, it has a sufficient bending rupture load as shown below. The porous electrode substrate of the present invention has a bending rupture load of at least 0.06 N in at least one direction even when the thickness is at most 150 μm. More preferably, even when the thickness is 130 m or less, a bending strength in at least one direction that exhibits a mechanical strength of 0.6 N or more. More preferably, it has a bending rupture load of 0.1N or more in at least one direction.

The bending rupture load in the present invention is a value obtained by a method in accordance with JIS K-6911, and represents the strength against bending fracture. The bending rupture load is a force whose value changes depending on the strain rate, the distance between fulcrums, and the width of the test piece. Is adopted. In the continuous production process of the porous electrode substrate or the production process of MEA (membrane-electrode assembly) using this porous electrode substrate, avoid problems such as cracks and tears in the handling of the product. In the above, it is preferable that the bending rupture load in the above one direction is 0.06 N or more.

In conventional porous electrode base materials, if the thickness is reduced, the generated gas cannot be discharged or becomes brittle, which often hinders handling in the above process.

As a method for improving the mechanical strength of the porous electrode substrate while maintaining a satisfactory gas permeability, there is a method of increasing the length of short carbon fibers, but uniform dispersion may be a problem. There was sex.

[0017] <Eye weight>

In the porous electrode substrate of the present invention, the basis weight (weight per unit area) of the carbon fibers needs to be 16 to 4 OgZm ² . At this time, it is preferable that two sheets of carbon fiber paper having half the basis weight are overlapped to obtain the above basis weight. The short carbon fibers are not only a conductive material but also serve as a reinforcing material for the porous electrode substrate.

By setting the basis weight of the carbon fiber to 16 gZm ² or more, the strength of the porous electrode It can be. Further, by setting the thickness to 40 gZm ² or less, the structure becomes excessively dense even when the thickness is set to 150 / zm or less.

In addition, the porous electrode substrate of the present invention can be continuously wound, which is preferable in terms of the porous electrode material / productivity and cost of the fuel cell. In particular, the porous electrode substrate of the present invention can be easily handled because its thickness can be reduced, and therefore, it is preferable that the substrate is continuously wound.

When the pore distribution of the porous electrode substrate of the present invention is measured by a mercury intrusion method, the volume per unit weight of pores having pore diameters of 5 m or less is 0.20 to: LOOccZg. Is preferred. Further, the pore volume of pores having a radius of 10 m or less is preferably 15% or more of the total pore volume, more preferably 20% or more.

The porous electrode substrate for fuel cells has a function to efficiently deliver the reaction gas to the reaction section (catalyst layer). Efficiently discharges the water contained in the reaction gas and the water generated by power generation. Function is required. In order to efficiently discharge water from the electrode base material, especially when the film thickness is thin, the radius of the pore is 5 m or less as a hole for temporarily taking in water when a large amount of water is generated. It is preferable that the volume per unit weight of the pores is 0.20 ccZg or more, or the pore volume of pores 10 m or less is 20% or more of the total pore volume. When short carbon fibers are reinforced by being cross-linked with filamentary fatty carbide, small pores are formed, and the volume per unit weight of pores with a radius of 5 m or less per unit weight is 0. It is possible that the pore volume of pores with a pore diameter of 20 ccZg or more and a pore radius of 10 m or less has 15% or more of the total pore volume. Alternatively, if the volume per unit weight of the pores having a pore radius of 5 μm or less is greater than 1. OOccZg, moisture is discharged to the outside, which is not preferable. The pore radius and the pore volume are calculated from the pressure in the measurement cell and the volume of mercury injected at that time.

[0019] <Roll type>

It is preferable that the porous electrode substrate of the present invention be wound around a paper tube having a diameter of 3 inches or less, since the equipment used for manufacturing and the packaged product can be compacted. If the paper tube size is small, it is easy to carry, which is also preferred. [0020] <Manufacturing method>

The method for producing the porous electrode substrate of the present invention is, for example, by the following method. That is, the production of a porous electrode base material in which a carbon fiber paper consisting of short carbon fibers having a fiber diameter of 3 to 9 μm and vinylon fibers and having a basis weight of 16 to 40 gZm ² is impregnated with resin and then carbonized. Method: Alternatively, impregnate resin into carbon fiber paper of 8 to ²⁰ gZm2 with carbon fiber mesh consisting of short carbon fiber having a fiber diameter of 3 to 9 m and vinylon fiber, bonding two sheets, and then carbonizing. This is a method for producing a porous electrode substrate.

[0021] Kuvinylon fiber>

In the production method of the present invention, it is necessary to use vinylon fibers. Vinylon fiber is a fiber in which heat resistance and water resistance are increased by heat treating or acetalizing formyl alcohol fiber with formaldehyde. The vinylon fiber is decomposed and lost by carbonization, but the shape of the resin adhered therearound remains as it is, and the resin forms a filamentous carbonized material.

The fineness of the vinylon fiber is not particularly limited, but is preferably 0.05 to 1.5 dtex. By setting the fineness to 0.05 dtex or more, adhesion of resin per vinylon fiber is sufficient, and it is possible to prevent filamentous resin carbide from peeling from the porous electrode substrate after carbonization. Can be. By setting the fineness to 1.5 dtex or less, it is possible to prevent the surface of the porous electrode substrate from becoming rough, and to make the contact between the porous electrode substrate and peripheral members favorable when the fuel cell is used. .

The length of the vinylon fiber is not particularly limited, but is preferably about the same as the short carbon fiber used at the same time. From the viewpoint of the binding property to the binder and the dispersibility, 2 to 12 mm is preferable. By dispersing together with carbon fibers, vinylon fibers also play a role in preventing reconvergence of carbon fibers. Therefore, those having excellent affinity for water are preferable.

The mass ratio of vinylon fibers in the carbon fiber paper is preferably 10 to 60% by mass. By setting the mass ratio of vinylon fibers in the carbon fiber paper to 10% by mass or more, filaments derived from vinylon fibers can be obtained. The reinforcing effect of the filamentary carbide is sufficient, while if it is 60% by mass or less, the balance between the filamentous carbide and the other carbides is good and the porous electrode substrate The form of the material can be satisfactory.

[0022] <Organic polymer compound>

The organic high molecular compound acts as a binder (glue) to hold each component in the carbon fiber paper. As the organic polymer compound, polyvinyl alcohol (PVA), polyvinyl acetate, or the like can be used. In particular, polybutyl alcohol is excellent as a binder in the papermaking process, and therefore, is less likely to drop short carbon fibers, and thus is preferred as a binder. In the present invention, the organic polymer compound can be used as a fibrous form.

As a papermaking method for carbon fiber paper, a wet method in which short carbon fibers are dispersed in a liquid medium to form a paper, or a dry method in which short carbon fibers are dispersed in air and deposited, can be applied. The method is preferred. Wet papermaking of vinylon fiber with the above amount and an appropriate amount of organic polymer material as a binder to help disperse the short carbon fibers into single fibers and prevent the dispersed single fibers from preventing convergence again Is preferred.

As a method of mixing short carbon fiber, vinylon fiber, and an organic polymer compound as required, there are a method of stirring and dispersing in water with short carbon fiber and a method of directly mixing.

In order to uniformly disperse 1S, a method of diffusing and dispersing in water is preferable. By mixing the organic polymer compound in this manner, the strength of the carbon fiber paper is maintained, and the carbon fiber paper strength is prevented from peeling off and the orientation of the carbon short fiber changing during the production. Can be prevented.

In addition, there are a continuous papermaking method and a batchwise papermaking method. In the present invention, the continuous papermaking method is particularly preferred in that the control of the basis weight is easy and the productivity and the mechanical strength are considered. ,.

[0024] Kupo fat>

The resin composition used as the resin in the present invention is a substance that remains as a conductive substance even after carbonization, and is preferably one that exhibits tackiness or fluidity at room temperature. Phenol resin, furan resin, epoxy resin, melamine resin, imide resin, urethane resin, aramide resin, pitch, etc. can be used alone or as a mixture. Phenol resins are preferred as they react with phenols and aldehydes in the presence of alkali catalysts. Thus, the obtained resole type phenol resin can be mentioned.

A resol-type phenol resin is prepared by dissolving a novolak-type phenol resin which shows heat-fusing property of a solid and is formed by the reaction of phenols and aldehydes under acidic catalyst by a known method. In this case, a self-crosslinking type containing a curing agent such as hexamethylenediamine is preferable.

As phenols, for example, phenol, resorcin, cresol, xylol and the like are used. As the aldehyde, for example, formalin, paraformaldehyde, furfural and the like are used. These can be used as a mixture. These can be used commercially as phenolic resins.

[0025] <Amount of fat>

The amount of the resin adhering to the carbon fiber paper is preferably 70 to 150 parts by mass with respect to 100 parts by mass of the short carbon fiber. As described above, in order to produce an electrode substrate with excellent bending strength, in which the supply and discharge of water and gas are performed smoothly, the ratio of the resin carbide in the porous electrode substrate is 25 to 40% by mass. It is necessary to adhere the resin so that 70 to 150 parts by mass of the resin must be adhered.

The method of impregnating the carbon fiber paper with the resin is not particularly limited as long as the carbon fiber paper can be impregnated with the resin, but the resin is uniformly coated on the surface of the carbon fiber paper using a coater. The method, dip-nip method using a squeezing device, or the method of superimposing carbon fiber paper and resin film and transferring the resin to carbon fiber paper can be performed continuously, and the productivity and long-length method can be used. If it can be manufactured, it is preferred.

[0027] <Hardening of resin, carbonization>

The carbon fiber paper impregnated with the resin can be carbonized as it is. However, it is preferable to cure the resin before carbonization in order to suppress the vaporization of the resin during carbonization and to improve the strength of the porous electrode substrate. For curing, any technique can be applied as long as it can uniformly heat the resin-impregnated carbon fiber paper. Examples of the method include a method of laminating and heating the upper and lower surfaces of carbon fiber paper impregnated with a resin, and a method of blowing hot air from both upper and lower surfaces, and a method of using a continuous belt device or a continuous hot blast stove. The cured resin is subsequently carbonized. Carbonization is performed in an inert gas to increase the conductivity of the porous electrode substrate. The carbonization is preferably performed continuously over the entire length of the carbon fiber paper. If the electrode substrate is long, not only will the productivity of the electrode substrate be increased, but also the subsequent process of manufacturing the Membrane Electrode Assembly (MEA) can be carried out continuously, thus reducing the cost of the fuel cell. Can be greatly contributed to.

In the carbonization, it is preferable to continuously perform the baking treatment over the entire length of the carbon fiber paper in a temperature range of 1000 to 3000 ° C. in an inert treatment atmosphere. In the carbonization of the present invention, the carbonization is performed before the carbonization treatment performed in an inert atmosphere at a temperature range of 1000 to 3000 ° C. and before the firing in an inert atmosphere of about 300 to 800 ° C. Processing may be performed.

It is preferable to include a step of heating the carbon fiber paper after adhering the resin to the carbon fiber paper and smoothing the surface of the carbon fiber paper. The method for smoothing the carbon fiber surface is not particularly limited! However, there is a method of hot pressing with a smooth rigid plate from both upper and lower surfaces, and a method of using a continuous belt press. Above all, a method using a continuous belt press device is preferred from the viewpoint of forming a long porous electrode substrate. If the porous electrode substrate is long, not only will the productivity of the porous electrode substrate increase, but also subsequent MEMBRANE ELECT RODE ASSEMBLY (MEA) production can be performed continuously, reducing fuel cell costs. This can greatly contribute to the dagger. Even when there is no step of smoothing the surface, a porous electrode substrate having both good strength and gas permeability can be obtained.However, since the porous electrode substrate has large undulations, the porous electrode substrate has a porous structure. The contact between the porous electrode substrate and the peripheral substrate is not sufficient, which is not preferable.

There are two types of pressing methods in continuous belt devices: a method of applying a linear pressure to the belt by a roll press and a method of pressing by a surface pressure by a hydraulic head press. The latter is a smoother porous electrode substrate. Is preferred in that is obtained. In order to effectively smooth the surface, it is best to press at a temperature at which the resin is most soft, and then fix the resin by heating or cooling. When the ratio of the resin impregnated in the carbon fiber paper is large, it is easy to make the carbon fiber paper smooth even if the pressing pressure is low. At this time, if the pressing pressure is increased more than necessary, the structure of the porous electrode substrate becomes too dense and the structure is severely deformed. This is not preferable because it causes problems such as the following. If the pressing pressure is too high and the density is too high, the gas generated at the time of firing may not be discharged well and the structure of the porous electrode substrate may be broken. When the resin impregnated in carbon fiber paper is cured by sandwiching it between rigid plates and using a continuous belt device, apply a release agent in advance to prevent the resin from adhering to the rigid plate and belt, or use a carbon fiber It is preferable that the separation be performed with a release paper between the paper and the rigid plate / belt.

[Third and fourth inventions]

Hereinafter, embodiments of the third and fourth inventions will be described with reference to the drawings.

Any of carbon fibers, pitch-based carbon fibers, rayon-based carbon fibers, and the like may be used, but polyacrylonitrile-based carbon fibers are preferred, and the particularly used carbon fiber is polyacrylonitrile (

It is preferable that only the PAN) -based carbon fiber be used because the mechanical strength of the porous carbon electrode substrate can be relatively high.

The diameter of the short carbon fiber is 3 ~ 9 / ζπι, the production cost of the short carbon fiber, the dispersibility, and the surface smoothness of the final porous carbon electrode substrate are also required. It is preferably 8 μm or less.

[0029] <Dispersion>

[0030] <Lead carbide>

Depending on the type of the resin and the amount of impregnation into the carbon fiber paper, the ratio of the resin carbide finally remaining as a carbide on the porous carbon electrode base material varies.

When the porous electrode base material is 100% by mass, the resin carbide in it is 25-40% by mass. More preferably, the lower and upper limits are preferably 28% by mass and 34% by mass, respectively.

In order to completely bind the short carbon fibers and keep the mechanical strength of the porous electrode substrate sufficient, 25% by mass or more of the resin carbide is required. The short carbon fibers that are not completely bound may fall off from the porous electrode base material, stick to the electrolyte membrane, and cause a short circuit. On the other hand, it is advantageous to keep the proportion of short carbon fibers in the porous electrode base material high, and set it to 40% by mass or less so that the pores are not filled with the resin due to the pressure applied during the curing of the resin. It is.

[0031] <Amorphous fatty carbide>

[0032] <Reticulated fatty carbide>

In the present invention, from the viewpoint of achieving both mechanical strength and reactive gas / moisture management together with the amorphous resin carbide, a network resin resin having a minimum fiber diameter of 3 m or less that crosslinks short carbon fibers with short carbon fibers. The existence of is required.

This reticulated carbonized carbide is different in appearance from short carbon fibers, and the carbon constituting the reticulated carbonized carbon has a very good orientation of the carbon arrangement in the short carbon fibers. Is the same as the above-mentioned resin carbide.

Fig. 1 shows how short carbon fibers and short carbon fibers are crosslinked with a network of fatty carbides with a minimum fiber diameter of 3 µm or less. By bridging a mesh-like resin carbide between short carbon fibers as shown in Fig. 1, both small holes with a diameter of about 2 m and large holes with a diameter of about 50 m can be mixed. The thin net-like resin carbide does not have a great reinforcing effect as compared with carbon fiber, but tends to reduce the gas permeability because the fine pores are finely divided. However, even when small holes absorb generated water under high humidification conditions, relatively large holes exist, so that gas does not flow and performance does not suddenly deteriorate (so-called flooding). The conventional porous electrode substrate having high gas permeability has a problem that the catalyst layer and the polymer film formed thereon are easily dried, but the porous electrode of the present invention having a network of crosslinked fatty carbon carbides. In the base material, reticulated carbides form many small pores, The stability of the supply and discharge of the reaction gas is also stable, so that the performance when assembled in a fuel cell can be improved.

When the distribution of the pore radius is measured by the mercury porosimetry, the porous electrode substrate of the present invention has a distribution peak at a pore radius of 10 μm or less and 50 μm or more. Is preferred. As a result, the porous electrode substrate of the present invention not only has a function of efficiently delivering the reaction gas to the reaction section (catalyst layer), but also has a function of efficiently discharging water contained in the reaction gas and water generated by power generation. Will have. In order to efficiently deliver the reaction gas to the reaction section (catalyst layer), the presence of pores having a radius of 50 m or more is effective.To discharge water efficiently, a large amount of water is generated. It is effective to have pores with a radius of 10 μm or less as pores for temporarily taking in moisture.

The porous electrode base material of the present invention is formed of a network of fat-carbon carbides in which large short pores formed by short carbon fibers and short carbon fibers bound by amorphous carbon carbides and short carbon fibers and carbon short fibers are formed. Since it has small pores formed by cross-linking, it is possible to have the above distribution of pore radii.

The gas permeability in the present invention is a value obtained by a method in accordance with JIS standard P-8117, and indicates the ease with which a porous electrode substrate can release gas. It can be calculated by sandwiching a porous electrode substrate between cells with a 3 mm diameter hole, flowing 200 mL of gas through the hole at a pressure of 1.29 kPa, and measuring the time it takes for the gas to permeate.

The gas permeability of the porous electrode substrate of the present invention is preferably 2000 mZsecZMPa or less, more preferably 1900 mZsecZMPa or less. In the porous electrode substrate of the present invention, the gas permeability is relatively small due to the presence of the mesh-like resin carbide. In order to increase the gas permeability of the porous electrode substrate of the present invention, it is necessary to reduce the force per unit area or the bulk density. In the present invention, by setting the gas permeability of the porous electrode base material to 2000 mZsecZMPa or less, it is difficult to break even if the basis weight is small, and even if the bulk density is small, the short carbon fiber does not stand in the thickness direction. It can be.

[0035] <Roll form> It is preferable that the porous electrode substrate of the present invention be wound around a paper tube having a diameter of 3 inches or less, since the equipment used for manufacturing and the packaged product can be compacted. If the paper tube size is small, it is easy to carry, which is also preferred.

[0036] <Manufacturing method>

The method for producing a porous electrode device according to the present invention is characterized in that a short carbon fiber having a fiber diameter of 3 to 9 / ζπι dispersed in a substantially two-dimensional plane in a random direction and a filter other than a fibrous fiber are provided. This is a method for producing a porous electrode base material in which a fibril-like material having a water power of 00 to 900 ml, a carbon fiber paper which is strong, is impregnated with resin, and then carbonized.

The point that the production cost can be reduced. It is preferable that the production of the porous electrode substrate be continuously performed throughout the entire process.

[0037] <Fibrils>

In the present invention, by the above-mentioned fatty carbide,

1) Short carbon fibers are bound together by irregular shaped fatty carbide

2) Crosslinked with mesh-like resin carbide with a minimum fiber diameter of 3 μm or less

Use fibrils to achieve a structured structure.

The fibril-like substance disappears due to carbonization of the resin, but the resin adhered around the fibril-like substance remains as a resin carbide and contributes to the formation of a network structure of the resin carbide.

It is necessary that the fibrils have a freeness of 400 to 900 ml and are other than fibrils. By setting the freeness to 400 ml or more, the surface condition of the porous electrode substrate can be improved. Also, when carbon fiber paper is produced by papermaking, the water drainage during papermaking is good. On the other hand, by setting the volume to 900 ml or less, the diameter of the fibers forming the fibril-like material can be made appropriate, and the fuel cell can be used in which the surface of the porous electrode substrate is not roughened. Good contact with other members can be maintained.

The fibril-like material is dispersed together with the short carbon fibers, and also plays a role in preventing the re-convergence of the short carbon fibers. In addition, some resins generate condensed water when the resin is cured, but the fibril-like material can be expected to absorb and discharge the water. Therefore, those having excellent affinity for water are preferable. Specific fibrils include fibrils Synthetic pulp such as modified polyethylene fiber, acrylic fiber, and aramide fiber is used. The fibrillated polyethylene fiber is also preferable in terms of affinity with carbon fiber, handleability, and cost. The fibril-like fibrous material remains as carbon on the porous electrode substrate when the resin is carbonized, so that it is difficult to form a network-like resin carbide.

When producing carbon fiber paper by papermaking, it is essential that the fibril-like material is insoluble and does not swell in the dispersion medium during papermaking. When a fibril-like substance that dissolves in a dispersion medium is used, a network-like resin carbide cannot be formed because the shape has already changed at the stage of adhering the resin.

It is preferable that the surface free energy of the fiber constituting the fibril-like material is larger than the surface free energy of the short carbon fiber used from the viewpoint of efficiently forming a crosslinked structure. Since the surface free energy of the fiber constituting the fibril-like material is larger than that of the short carbon fiber, the impregnated resin adheres preferentially to the fiber, and a carbon-like crosslinked structure is easily formed after carbonization.

The weight ratio of the fibril-like material in the carbon fiber paper is preferably from 10 to 70% by mass. By setting the fibril-like material to 10% by mass or more, a network-like resin carbide can be sufficiently developed, and sufficient mechanical strength and gas permeability can be imparted to the porous electrode substrate. Further, the fibril-like material is preferably 10% by mass or more in order to act as a reinforcing material for overcoming an external force such as undulation generated when the resin is cured under pressure. On the other hand, if the fibril-like material is set to 70% by mass or less, it is possible to prevent the porous electrode base material from easily collapsing due to insufficient resin adhering to the short carbon fiber, and preventing the thickness control from becoming difficult.

In the method for producing a porous electrode device of the present invention, an organic high molecular compound can be added as a constituent material of the carbon fiber paper. Organic polymer compounds act as binders to hold the components together in carbon fiber paper. As the organic high molecular compound, polyvinyl alcohol (PVA), polyacetic acid butyl, and the like can be used. Among them, polybutyl alcohol, polyacrylonitrile, cellulose, polyacetate butyl and the like are preferably used. In particular, polybutyl alcohol has excellent binding power in the papermaking process, so the short carbon fibers fall off. And is preferred as a binder. In the present invention, the organic polymer compound can be used as a fibrous form.

[0039] <Paper making of carbon fiber paper>

Carbon fiber paper is suitably obtained by papermaking. As the papermaking method, a wet method of dispersing short carbon fibers in a liquid medium to form a paper, or a dry method of dispersing short carbon fibers in air and depositing them can be applied. Among them, the wet method is preferable. In addition, as described above, it is necessary to mix an appropriate amount of fibril-like synthetic fibers that play a role in preventing the opening and reconvergence of short carbon fibers, and an appropriate amount of a binder as a binder for binding short carbon fibers. It is preferable to mix organic polymer substances.

There are two methods for mixing the fibril-like substance and, if necessary, the organic high molecular compound into the short carbon fibers: a method of stirring and dispersing in water together with the short carbon fibers and a method of directly mixing the same. Is preferably a method of diffusing and dispersing in water. By mixing the organic polymer compound in this manner, the strength of the carbon fiber paper is maintained, and the carbon fiber paper strength is prevented from peeling off and the orientation of the carbon short fibers changing during the production. Can be prevented.

Further, papermaking may be performed continuously or batchwise. In the present invention, continuous papermaking is preferred, particularly in that the weight per unit area is easily controlled and productivity and mechanical strength are considered. .

[0040] <榭脂>

The resin composition used as the resin in the present invention is preferably a phenol resin, a furan resin, which is a substance which exhibits tackiness or fluidity at room temperature and which remains as a conductive substance even after carbonization. Epoxy resin, melamine resin, imide resin, urethane resin, aramide resin, pitch and the like can be used alone or as a mixture. As the phenol resin, a resole type phenol resin obtained by reacting a phenol and an aldehyde in the presence of an alkali catalyst can be used.

In addition, a novolak type phenolic resin which is formed by the reaction of phenols and aldehydes under acidic catalyst by a known method and which is a solid heat-fusible phenolic resin is dissolved and mixed into the resole type phenolic resin. In this case, a hardener, for example For example, a self-crosslinking type containing hexamethylene diamine is preferable. As phenols, for example, phenol, resorcin, cresol, xylol and the like are used. As the aldehyde, for example, formalin, paraformaldehyde, furfural and the like are used. These can be used as a mixture. These can be used commercially as phenolic resins.

[0041] <Amount of fat>

The amount of the resin adhering to the carbon fiber paper is such that 70 to 120 parts by mass of the resin adheres to 100 parts by mass of the short carbon fiber. As described above, in order to supply and discharge water and gas smoothly and produce an electrode substrate with excellent bending strength, resin should be applied so that the ratio of resin carbide is 20 to 30% by mass. To keep 70-120 parts by weight of resin.

[0042] <Method of impregnating fat>

The carbon fiber paper impregnated with the resin can be carbonized as it is. However, it is preferable to cure the resin before carbonization in order to suppress the vaporization of the resin during carbonization and to improve the strength of the porous electrode substrate. For curing, any technique can be applied as long as it can uniformly heat the resin-impregnated carbon fiber paper. Examples of the method include a method of laminating and heating the upper and lower surfaces of carbon fiber paper impregnated with a resin, and a method of blowing hot air from both upper and lower surfaces, and a method of using a continuous belt device or a continuous hot blast stove. The cured resin is subsequently carbonized. Carbonization is performed in an inert gas to increase the conductivity of the porous electrode substrate. The carbonization is preferably performed continuously over the entire length of the carbon fiber paper. If the electrode substrate is long, not only will the productivity of the electrode substrate be increased, but also the subsequent process of manufacturing the Membrane Electrode Assembly (MEA) can be carried out continuously, thus reducing the cost of the fuel cell. Can be greatly contributed to. In the carbonization, it is preferable to continuously perform the baking treatment over the entire length of the carbon fiber paper in a temperature range of 1000 to 3000 ° C. in an inert treatment atmosphere. In the carbonization of the present invention, the carbonization is performed before the carbonization treatment performed in an inert atmosphere at a temperature range of 1000 to 3000 ° C. and before the firing in an inert atmosphere of about 300 to 800 ° C. Processing may be performed.

There are two types of pressing methods in continuous belt devices: a method of applying a linear pressure to the belt by a roll press and a method of pressing by a surface pressure by a hydraulic head press. The latter is a smoother porous electrode substrate. Is preferred in that is obtained. In order to effectively smooth the surface, it is best to press at a temperature at which the resin is most soft, and then fix the resin by heating or cooling. When the ratio of the resin impregnated in the carbon fiber paper is large, it is easy to make the carbon fiber paper smooth even if the pressing pressure is low. At this time, it is not preferable to increase the pressing pressure more than necessary, because when the porous electrode base material is used, the structure becomes too dense or the structure is severely deformed. If the pressing pressure is too high and the density is too high, the gas generated at the time of firing may not be discharged well and the structure of the porous electrode substrate may be broken. When the resin impregnated in carbon fiber paper is cured by sandwiching it between rigid plates and using a continuous belt device, apply a release agent in advance to prevent the resin from adhering to the rigid plate and belt, or use a carbon fiber It is preferable that the separation be performed with a release paper between the paper and the rigid plate / belt. Example

Hereinafter, the first and second inventions will be described in Examples 1 to 5 (Comparative Examples 1 and 2), and the third and fourth inventions will be described in Examples 6 to 10.

(Comparative Examples 3 to 7) will be described more specifically.

Each physical property value in the examples was measured by the following methods.

[0045] 1) Bending rupture load

Cut 10 pieces of 80 x 10mm size so that the longitudinal direction of the carbon fiber paper in the porous electrode substrate at the time of papermaking is the long side of the test piece. Using a bending strength tester, the distance between the fulcrums was set to 2 cm, a load was applied at a strain rate of lOmmZmin, and the load when the test piece broke was measured. It is the average value of 10 test pieces.

[0046] 2) Gas permeability

It is determined by a method based on JIS standard P-8117. A test piece of a porous electrode substrate is sandwiched between cells having a hole of 3 mm in diameter, and 200 mL of gas is flowed through the hole at a pressure of 1.29 kPa, and the time required for gas permeation is measured. It was calculated from:

Gas permeability (m / sec / MPa)

= Gas permeation amount (m ³ ) Z Gas permeation pore area (m ² ) Z permeation time (sec) Z permeation pressure (MPa) [0047] 3) Average pore radius of electrode substrate · Total pore volume · Radius 10 Volume of pores with a radius of 5 μm or less

The pore distribution of the pore volume and the pore radius was determined by the mercury intrusion method, and the radius at which 50% of the pore volume was shown was defined as the average pore diameter of the electrode substrate. The mercury porosimeter used was Pore Master-60 manufactured by Quantachrome.

[0048] 4) Thickness

The thickness of the porous electrode substrate was measured using a thickness measuring device dial thickness gauge 7321 (manufactured by Mitutoyo). The size of the probe at this time was 10 mm in diameter and the measurement pressure was 1.5 kPa.

[0049] 5) Sheet resistance

Cut the carbon fiber paper in the porous electrode substrate to a size of 100 x 20 mm so that the longitudinal direction of the paper at the time of papermaking is the long side of the test piece. A copper wire was placed on one side of the electrode substrate at an interval of 2 cm, and the resistance was measured when a current was applied at a current density of 10 mAZcm ² . [0050] 6) Penetration direction resistance

The electric resistance in the thickness direction of the porous electrode substrate (through-hole resistance) is measured by inserting a sample between copper plates, applying pressure from above and below the copper plate with IMPa, and applying a current with a current density of lOmAZcm ^2. Then, it was obtained from the following equation.

Penetration resistance (Ω.cm ² ) = Measured resistance value (Ω) X Sample area (cm ² )

[0051] 7) Weight ratio of fat carbide

The weight ratio of the fatty carbide was calculated from the following formula, the basis weight of the obtained porous electrode base material and the basis weight of the short carbon fiber used.

榭 Carbide weight ratio (% by mass)

= [Basis weight of porous electrode substrate (gZm ² )-basis weight of short carbon fiber (gZm ² )] X 100 ÷ weight of porous electrode substrate (gZm ² )

(Example 1)

As short carbon fibers, polyacrylonitrile (PAN) carbon fibers having an average fiber diameter of 7 m and an average fiber length of 3 mm and PAN-based carbon fibers having an average fiber diameter of 4 μm and an average fiber length of 3 mm are 70:30 ( (Mass ratio) were prepared.

As the vinylon fiber, 1. ldtex, vinylon short fiber (cutica vinylon F, manufactured by UTICA Ltd.) having a cut length of 5 mm was prepared.

As the organic polymer compound, short fibers of polybutyl alcohol (PVA) (VBP105-1 manufactured by Kuraray Co., Ltd., cut length 3 mm) were prepared.

The short carbon fibers are dispersed uniformly in water in a slurry tank of a wet-type short net continuous papermaking machine, disintegrated into single fibers, and when sufficiently dispersed, the PVA short fibers and vinylon short fibers are reduced to 100 parts by mass of short carbon fibers. On the other hand, they were uniformly dispersed so as to be 18 parts by mass and 32 parts by mass, respectively, and sent out in a web form.

The fed web was passed through a short netting plate, dried with a drier, and a carbon fiber paper having a basis weight of 20 g / m ² and a length of 100 m was obtained (the basis weight of each composition is described in Table 1, the same applies hereinafter). The dispersion state of each fiber was good.

Next, the carbon fiber paper was evenly spread on a roller to which a methanol solution of phenol resin containing 40% by mass of phenol resin (Deno Nippon Chemical Co., Ltd. phenolite J-325) was attached. After contacting one surface at a time, hot air was blown continuously and dried. A resin-adhered carbon fiber paper of 32 g / m ² was obtained. This means that 90 parts by mass of the phenol resin adhered to 100 parts by mass of the short carbon fibers.

Next, after adhering two pieces of the resin-attached carbon fiber paper so that the surface in contact with the short netting faces outward, a continuous heating press device equipped with a pair of endless belts (a double belt press device). : DBP) to obtain a sheet having a smooth surface (sheet thickness: 110 πι, width 30 cm, length 100 m).

Preheating temperature 200 ° C in the preheating zone of this time, the preheating time is 5 minutes, heating圧Zo over emissions at temperatures 250 ° C, pressing pressure at a linear pressure of 8. OX 10 ⁴ N / m there were. The sheet was inserted between two release papers so that the sheet did not stick to the belt.

Thereafter, the obtained sheet was heated in a continuous firing furnace at 500 ° C. for 5 minutes in a nitrogen gas atmosphere to cure the phenol resin and precarbonize. Subsequently, the obtained sheet was heated in a continuous firing furnace at 2000 ° C. for 5 minutes in a nitrogen gas atmosphere to be carbonized, thereby continuously obtaining an electrode substrate having a length of 100 m. It was wound up on a paper tube. Although thin, it was an electrode substrate that was smooth and excellent in handling, immediate bending strength and gas permeability. The evaluation results are shown in Tables 2 and 3. Fig. 11 shows an SEM photograph and Fig. 2 shows the pore distribution.ため Because of the presence and absence of cross-linked portions of gallium carbide, the distribution range of pores is widened, and the pore volume of pores with a pore radius of 10 m or less accounts for 30% of the total pore volume Was.

(Example 2)

A porous electrode substrate having a smooth surface was obtained in the same manner as in Example 1, except that the ratio of the short carbon fibers was changed to 50Z50 (mass ratio). The evaluation results are shown in Tables 2 and 3.

(Example 3)

A porous electrode substrate having a smooth surface was produced in the same manner as in Example 1 except that vinylon fibers were replaced with 0.6 dtex and vinylon staple fibers having a cut length of 5 mm (unitika vinylon F manufactured by UTICA Co., Ltd.). Got. The evaluation results are shown in Tables 2 and 3.

(Example 4)

In addition to the basis weight of vinylon fibers was replaced by the addition amount such that the LOgZm ² Example 3 A porous electrode substrate having a smooth surface was obtained in the same manner as in the above. The evaluation results are shown in Tables 2 and 3.

(Example 5)

A porous electrode substrate having a smooth surface was obtained in the same manner as in Example 1, except that only PAN-based carbon fibers having an average fiber diameter of 4 / zm and an average fiber length of 3 mm were used as the short carbon fibers. The evaluation results are shown in Tables 2 and 3.

(Comparative Example 1)

As short carbon fibers, the average fiber diameter of 7 / ζ πι, using the average fiber length of only PAN-based carbon fibers of 3 mm, except that no添Ka卩vinylon fibers, in the same manner as in Example 1, 15 g / m ² Of carbon fiber paper was obtained. In the same manner as in Example 1, 100 parts by mass of phenol resin was adhered to 100 parts by mass of carbon fiber short fibers to obtain 28 gZm ² of resin-adhered carbon fiber paper.

Thereafter, an attempt was made to obtain a porous electrode substrate in the same manner as in Example 1. However, under the same conditions as in Example 1, after heating and pressurizing, countless screens entered.When the preheating temperature was increased to 200 ° C and the power was increased to 230 ° C, the screen disappeared. Then, firing was performed in the same manner as in Example 1 to obtain a porous electrode substrate. The obtained porous electrode substrate was brittle and difficult to handle. Tables 2 and 3 show the evaluation results. FIG. 2 shows the pore distribution of the porous electrode substrate. Since the peak is sharp and the pore volume of pores of 10 m or less is only 19% of the total pore volume, it is expected that the performance will be low even when incorporated into a cell where the generated moisture is difficult to control. .

(Comparative Example 2)

The basis weight of the carbon fiber paper 30GZm ^2, except that the basis weight of榭脂on carbon fiber paper in 56GZm ² is to obtain an electrode substrate in the same manner as in Comparative Example 1. The porous electrode base material became stronger due to the increased basis weight, but became brittle and difficult to handle. Tables 2 and 3 show the evaluation results.

[Table 1] Experimental examples of the first invention and the second invention

[Table 2]

Experimental examples of the first invention and the second invention

[Table 3] Experimental examples of the first invention and the second invention

Hereinafter, the third and fourth inventions will be described more specifically with reference to Examples 6 to 10 (Comparative Examples 3 to 7). (Example 6)

Polyacrylonitrile (PAN) -based carbon fiber with an average fiber diameter of 7 μm and an average fiber length of 3 mm and PAN-based carbon fiber with an average fiber diameter of 4 μm and an average fiber length of 3 mm 50:50 (mass ratio) To prepare short carbon fibers mixed.

Further, as a fibril-like material, polyethylene pulp (manufactured by Mitsui Irigaku Co., Ltd., SWP freeness 450 ml, pulp freeness test method of JIS P8121 (1) measured by Canadian standard type) was prepared.

The carbon short fibers are uniformly dispersed and defibrated in water in a slurry tank of a wet short net continuous paper making apparatus, and when sufficiently dispersed, 13 parts by mass of PVA short fibers and polyethylene pulp are added to 100 parts by mass of carbon short fibers. Parts and 38 parts by mass, and then distributed.

The fed web was passed through a short netting board and dried with a dryer to obtain a carbon fiber paper A having a basis weight of 28 g / m ² and a length of 100 m (the basis weight of each composition is described in Table 1, the same applies hereinafter). Dispersion is good and it is good.

Next, carbon fiber paper A is uniformly applied to a roller to which a 40% by mass methanol solution of phenol resin (Phenolite J-325, manufactured by Dainippon Ink and Chemicals, Inc.) has adhered. Then, hot air was blown continuously and dried. A resin-adhered carbon fiber paper having a basis weight of 47 g / m ² was obtained. At this time, 100 parts by mass of the phenol resin was adhered to 100 parts by mass of the short carbon fibers.

Next, two sheets of this resin-adhered carbon fiber paper were bonded together and continuously heated by a continuous heating press device (double belt press device: DBP) equipped with a pair of endless belts to smooth the surface. I got a sheet. (Sheet thickness: 200 m, width: 30 cm, length 100 m) At this time, the preheating temperature in the preheating zone is 150 ° C, the preheating time is 5 minutes, and the temperature in the heating and pressing zone is 250 ° C. Press pressure was linear pressure 8. OX 10 ⁴ N / m. The DBP was passed between two release papers so that the sheet did not stick to the belt.

Thereafter, the sheet is cured in a continuous firing furnace at 500 ° C for 5 minutes in a nitrogen gas atmosphere, pre-carbonized, and then continuously fired at 2000 ° C in a nitrogen gas atmosphere. , And continuously carbonized to obtain an electrode substrate having a length of 100 m, which was wound around a cylindrical paper tube having an outer diameter of 30 cm. The dispersion of the carbon fibers was good, and it was easy to handle and use as an electrode substrate. The evaluation results are shown in the table.

(Example 7-: L0)

Except for the conditions described in Table 4, the same operation as in Example 6 was performed to obtain a porous electrode device having a smooth surface. Table 5 shows the evaluation results. FIG. 8 shows the pore distribution of the porous electrode substrate obtained in Example 8. Two peaks are observed due to the presence of the reticulated carbide, and the distribution range of the pores is widened. Further, a single cell of a polymer electrolyte fuel cell was prepared using the porous electrode substrate, and the cell characteristics were evaluated. As a result, stable performance was obtained under the humidifying condition of 80 ° C. The results are shown in FIG.

(Comparative Example 3)

A carbon fiber paper having a basis weight of 26 g / m ² and a length of 100 m was obtained in the same manner as in Example 7, except that the amount of polyethylene pulp added was changed to 0. The dispersion state was good. Next, a resin-attached carbon fiber paper having a basis weight of 48 gZm ² was obtained in the same manner as in Example 7. Thereafter, an electrode substrate was obtained in the same manner as in Example 7. The gas permeability is excellent. It is brittle, and the fibers fall off.

(Comparative Example 4) No. 《Slurry adjusted so that the short fiber of polybutyl alcohol is 15 parts by mass with respect to 100 parts by mass of carbon short fibers in a paper making device of Tsutsumi, stir and stir, and remove carbon fiber paper of 30 gZm ^2. Obtained. In addition, 150 parts by weight of phenol resin was adhered to 100 parts by mass of carbon fiber short fibers to obtain a resin-adhered carbon fiber paper having a basis weight of 69 g / m ² . Two sheets of this resin-adhered carbon fiber paper were laminated and pressed at 180 ° C for 10 minutes at 0.2 MPa to cure the resin. This was carbonized at 2,000 ° C. in an inert gas to obtain an electrode substrate. The sample had low resistance and high gas permeability. However, when the battery characteristics were compared with the sample of Example 3, the performance was very high. As can be seen from the pore distribution, it is considered that this result was obtained because the electrode base material has few small pores and the water management ability in the electrode is not so high.

(Comparative Example 5)

An electrode substrate was obtained in the same manner as in Example 1, except that wood pulp (freeness: 550 ml) was used as the fibril-like material. Although the electrode substrate had a smooth surface, the force can also be seen from Fig. 2.This electrode substrate has few small holes, so the ability to manage the water in the electrode is not very high, so the performance when used as a battery Is not very high. The evaluation results are shown in the table.

(Comparative Example 6)

An electrode substrate was obtained in the same manner as in Comparative Example 3, except that polyacrylonitrile (PAN) -based carbon fibers having an average fiber diameter of 4 m and an average fiber length of 3 mm were used as the short carbon fibers. Force that was an electrode substrate with a smooth surface This electrode substrate is small and has few pores, so the ability to manage water in the electrode is not very high, so the performance when used as a battery is not very high. The evaluation results are shown in the table.

(Comparative Example 7)

An electrode substrate was obtained in the same manner as in Comparative Example 3, except that hemp pulp (freeness 350 ml) was used as the fibril-like material. Force that was an electrode substrate with a smooth surface This electrode substrate has a small number of small holes, so the ability to control the water content in the electrode is not very high, so the performance of a battery is not very high. The evaluation results are shown in the table.

[Table 4] Experimental examples of the third and fourth inventions

Five]

Industrial applicability

[0071] The first invention and the second invention overcome the problems of the prior art, and are inexpensive, compact, and optimal for a polymer electrolyte fuel cell electrode assembly in a cell stack. This is a method for producing a base material.

[0072] The porous electrode substrate of the third invention is inexpensive and smoothly supplies and discharges water and gas used for the reaction, and is capable of exhibiting cell performance. An electrode substrate can be obtained, and the fourth invention is a method for inexpensively producing this porous electrode substrate.

Claims

The scope of the claims

[1] Short carbon fibers having a fiber diameter of 3 to 9 m dispersed substantially in a random direction within a two-dimensional plane are bound together by an amorphous fatty carbide. A porous electrode substrate with a thickness of 150 m or less, cross-linked by a state-like resin carbide.

[2] Carbon fiber basis weight consisting of short carbon fibers with a fiber diameter of 3 to 9 μm and vinylon fibers 16 to

A method for producing a porous electrode substrate in which carbon fiber paper of 40 gZm ² is impregnated with resin and then carbonized.

[3] A porosity that impregnates carbon fiber paper with a carbon fiber weight of 8 to ² OgZm ² consisting of short carbon fiber with a fiber diameter of 3 to 9 μm and vinylon fiber with resin and stacks ^two sheets before carbonizing. Method for manufacturing porous electrode substrate.

[4] Short carbon fibers having a fiber diameter of 3 to 9 m dispersed in a random direction in a substantially two-dimensional plane are bound to each other with an amorphous fatty carbide, and the short carbon fibers are the smallest fibers. A porous electrode substrate with a diameter of 3 μm or less and cross-linked with mesh-like resin carbide.

[5] Short carbon fibers having a fiber diameter of 3 to 9 μm dispersed in a random direction in a substantially two-dimensional plane, and fibrous materials having a freeness of 00 to 900 ml other than fibrous fibers A method for producing a porous electrode substrate, comprising impregnating a carbon fiber paper made of a resin with a resin and then carbonizing the resin.